Vane pumps conventionally include a rotor coupled to an input shaft, a plurality of radial vanes carried by the rotor, side plates disposed on axially opposed sides of the rotor, and a cam ring carried between the side plates circumferentially surrounding the rotor. A plurality of fluid chambers are defined between the angularly spaced vanes, the axially spaced side plates and the radially spaced rotor and cam ring surfaces. A housing includes inlet and outlet passages for feeding hydraulic fluid to and from the chambers. Pressure applied to the pump creates a reaction torque on the cam ring, which must be absorbed by the surrounding housing. A similar reaction torque is created in vane-type hydraulic motors, in which flow of fluid through the housing and chambers provides a rotary output at the machine shaft.
It is a general object of the present invention to provide structure between the cam ring and the surrounding housing for absorbing the reaction torque caused by pressure applied to the pump. Another and more specific object of the present invention is to provide such torque-absorbing structure that is inexpensive, reliable, and can be readily implemented in vane-type machines of differing designs and constructions. Yet another object of the present invention is to provide torque-absorbing structure of the described character implemented in cartridge-type vane machines, which are currently preferred in the art, and/or which is adapted to be employed in machines for rotation in either direction. Yet another object of the invention is to provide a method of assembling machines of the described character.
A fixed displacement vane-type hydraulic machine in accordance with a presently preferred embodiment of the invention comprises a rotor, a plurality of vanes carried by the rotor, side plates on opposed sides of the rotor, and a cam ring carried between the side plates surrounding the vanes and rotor to define fluid chambers between the vanes. A housing surrounds and encloses the side plates and cam ring, and provides inlet and outlet passages for feeding fluid to and from the inter-vane chambers. A shaft is coupled to the rotor and extends from the housing. A cam pin (or key) extends radially between the cam ring and the housing surrounding the cam ring for preventing rotation of the cam ring with respect to the housing so as to absorb reaction torque on the cam ring with respect to the housing due to pressure applied to the pump. In the preferred embodiment of the invention, the cam pin is affixed to the cam ring, and is slidably received within an axial pocket in the surrounding housing during assembly of the cartridge to the housing. The axial pocket may comprise either a portion of the fluid flow path that extends through the housing, or a pocket specially formed in the housing for receiving the cam pin.
In the preferred embodiment of the invention, angularly spaced pins are affixed to and project radially from the cam ring. One of these pins is dimensioned for sliding fit with the surrounding housing during assembly. The other pin functions to locate the cam ring with respect to the housing, and thereby to prevent angular misalignment of the cam ring and the housing. The pins and slots do allow for reverse rotation of the pump mechanism within the housing.